The present invention relates to a SHEET FOR INK JET-RECORDING for use in forming recorded images using liquid ink such as water-based ink and, in particular, to a sheet for ink jet-recording (an INK JET-RECORDING SHEET), which never undergoes any color change during or after long-term storage, which is a disadvantage observed for the conventional ink jet-recording sheet, while maintaining such advantages that it can ensure a high density of full color-printed images formed thereon and that it is excellent in ink absorptivity.
The ink jet-recording system, in which images are formed by injecting water-based ink on a recording medium through a fine nozzle, has widely been used in, for instance, printers for terminal devices, facsimiles, plotters or devices for printing account books and slips. This is because, for instance, it has a low noise level during recording operations; it easily permits the color printing; it also permits high-speed recording; and it is less expensive as compared with other printing devices.
On the other hand, printers have rapidly been popularized recently and they have increasingly been required to give finer and more precise images at a high speed. In addition, there has recently been developed a digital camera. Correspondingly, recording mediums have been required to have higher recording characteristic properties. More specifically, there has been desired for the development of a recording medium, which is not only excellent in ink absorptivity, recording density, water resistance and storability, but also has image quality and shelf life almost comparable to those observed for the images formed on the silver halide system.
To satisfy such requirements, there have been proposed a large number of sheets each comprising a substrate provided thereon with an ink-receiving layer, which mainly comprises a pigment and a binder. For instance, there have been reported a variety of methods for applying, onto substrates, a coating layer comprising amorphous silica and a polymer binder (Japanese Un-Examined Patent Publication (hereunder referred to as “J.P. KOKAI” No. Sho 55-51583, J.P. KOKAI No. Sho 57-157786 and J.P. KOKAI No. Sho 62-158084); a coating layer comprising an ink-adsorbing pigment such as zeolite (J.P. KOKAI No. Sho 56-144172); a coating layer comprising finely pulverized silicic acid and a water-soluble resin (J.P. KOKAI No. Sho 56-148583); and a coating layer comprising a porous and cationic alumina hydrate (J.P. KOKAI No. Sho 60-232990).
Moreover, there have also been proposed methods, which comprise incorporating, for instance, cationic polymers (J.P. KOKAI No. Sho 56-84992, J.P. KOKAI No. Sho 60-49990 and J.P. KOKAI No. Sho 61-125878); and basic latexes (J.P. KOKAI No. Sho 57-36692) into the ink-receiving layers, in order to improve the water resistance of printed letters.
Furthermore, there have also been proposed, for instance, methods, which comprise adding, to the ink-receiving layer, at least one member selected from the group consisting of metal oxides and metal chlorides such as phosphorus tungstate, phosphorus molybdate and chromic chloride, and tannic acid (J.P. KOKAI No. Sho 57-87987); an antioxidant such as a hindered phenol (J.P. KOKAI No. Sho 57-74192); hindered amines (J.P. KOKAI No. Sho 61-146591); UV light absorbers such as benzophenone type, benzotriazole type and phenyl salicylic acid type ones (J.P. KOKAI No. Sho 57-74193, J.P. KOKAI No. Sho 57-87988 and J.P. KOKAI No. Sho 63-222885); a thiourea type compound (J.P. KOKAI No. Sho 61-163886); a specific mercapto compound such as 2-mercaptobenzothiazole and 2-mercaptobenzimidazole (J.P. KOKAI No. Sho 61-177279); and a dithiocarbamic acid salt, a thiuram salt, a thiocyanic acid ester or a thiocyanic acid salt (J.P. KOKAI No. Hei 7-314882).
However, the full color ink jet recorded images formed according to these techniques suffer from a problem of color change during a long-term storage and in particular, when a phthalocyanine dye is used as the dye for cyan color ink, these techniques have still been insufficient since the images cause color change along with the discoloration of the phthalocyanine dye.